Speed control for capacitor-run motors



May 29, 1951 2,554,956

J. B. REEVES SPEED CONTROL FOR CAPACITOR-RUN MOTORS Filed Feb. 18, 1950m a T /woym s Patented May 29, 1951 James 'B-z -lteevea w liitefish Bay,Wis.', assignonto (inner-Hammer, -Inc., Milwaukee, .Wis.,-. acorporationnfinclaware Application February. 18, 1950,Seria'lN02'144,91'1

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This invention relates" tir speed" control for" capacitor=run"motorsfThespeed" control" herein disclosed is in certain respects similar tothat .disciosedin 'the- Jones andReeves application; seria1 -Nm-93;-142;filed 13," 1949;- an'dis'an improvement thereon:

While not limited thereto;- tlie present inven' can isparticuIarIyapplicablefor governing operation of capacitor rurr motors whendrivingwindingor reelingd'evicessuc'li as =are used in the packagingof textilethread? Aprimary=object"of"tlie*invention=isto provide"- controlof asimple; sensitive I and reliablechar acter for controlling tlie speed ofmotors oi the aforementionedtype so tliatthey will =provide -forreelingor lengths of matcrialat substantiallyconstanttensiom Other- 'objectsand -advantages of the invention: will hereinafter appean The:accompanying drawingsnllustrater a: me ferredz: embodimentiofs the:invention which' will now: be described; it; being understood.:-thattthe, embodiment illustrated: isz-susceptible of: variousmodifications without: departingsfrom'v-r the scope oi the.appended-claims;

V In.thes-drawings;

' Eigurel, whichisdnpart: diagrammatic and, in; part schematic,-,illustratessaf' controltsystem efor motordriven"thread:windinggapparatus:embodg ingimy invention, and

Fig. 2. graphically illustrates the time phaserre-- lationship ofvoltagesr-existing in an:zelem'ent i of: the rcontrolssystemnf Rig. 1:.-

Referring; to Fig; lz,-,;itsho.ws: a'rmotor-driven. thread-windercomprisingoia? reekort' bobbin l on. which. a length of; thread: I ,l Iis; to bew wounclabye means of a1 capacitor-rum alternating; currentmotor: l2-which: drives- 'bobbin 'l Ihthrough a shaft. l3; The thread His: shown as.- being; supplied from. aespool I lwhich-may herezbeassumed; tabedriven" by known meansein a manner -'to.-insure: a:constant-'let off speed? of: thecthreamwith respect thereto;

Idler rollers: l5 and llivare suitably:placedrin thepath of threadsbetween-spool Il andxbobb'in- I E ta-facilitate. the formationxofi aloop or: festoon l-winvthread; Il= whichipasses through-a thread.- guideor: eyelet I 1-*secured:to a-:.tension arm I lia of. a' control device:I9; Tension-. arm I81 is none rotatably securedto. a--shafti-oficontroldevice' minal T? and. is-cOimecUed oHeterminaI ofacapacitor 22 throughits end terminal T Capacitor 22 has connectionthrough its other terminal;

to-supply line-L Winding l2 -also has connection through its endterminalT in serieswith a-current limiting" resistor 24, with thetanode 23. ofagastriode tube 23. Tube 23is providedwithl a cathode 23 which hasconnection with supply line L and a control electrode 23 through thevmedium of which: its conductor iscontrolled.

Control-electrode 23 of tube" 23 isconnected,

in 'seriesewith a resistor 26 and an adjustable-re sistance' 21,- to ahigh potential terminal A of Autotransformer is, also provided withterminals A? and A which; have' connection with supply lines L andLLre-- an autotransformer 25.

spectively;

saturable' reactor 28 is" provided with differentially connectedalternating currentwindings=28 and which are interconnected throughtheir respective end terminals 29 and 30 Winding 29 has connectionthrough its end terminal 29 withsupply line L and winding 3:0 has:

connection through its end terminal 30 with a poi-nt'common betweenresistor:'26 and adjustable resistance 21. Reactor 28'also has, forcontrolling.

its .degree of saturation, a winding 3i which is supplied withenergizing current derived from the output'coil32' of control device l9.

One end of 0011 32 of'control device I9 is conneoted,- in series with ahalf wave rectifier 33, to

one end of saturating-winding 3|, and the otherend of coil 32 isconnected to the other end of' coil 35] which is connected at one end tosupply $11118 L andat its other end to supply line L Controldevice l Sisfurther provided with an arm 36- which is non-rotatably secured to shaft20 andis adapted to assume various angular posi- 35. A- frame 31 (shownin broken lines) is-provided to support the aforedescribed components ofcontrol .device IS. The arm 36 andframe 3'! are 1 preferably formed of amagnetic material such as soft steelto-provide a low reluctance path forth'e magnetic flux induced by energization of coil 35. is sliownanddescribed in detail in the Jones and Reeves patent application, SerialNo. 36,718, filed Ju1y=2, 1948, which application also describes-thecharacteristics and behavior of the device.

Acapacitor 38 is preferably connected between control electrode 23 oftube 23- and line L to provide-for suppression of transient currents inf a well known manner;

A preferred form of control device 19 As will be apparent to thoseskilled in the art, adjustable resistance 21 inclusive of itsconnections with autotransiormer 25, constitutes one side of aphase-shift network for the control electrode 23 of tube 23 while thesaturable reactor 28 and the control device l9 inclusive of theirinterconnections aforedescribed, constitutes the other side of the samephase-shift network. Through the medium of this phase-shift network,control electrode 23 of tube 23 is subjected to an alternating currentpotential of substantially constant amplitude which is varied intime-phase relation with respect to the potential of anode 23 of tube 23in accordance with the degree of magnetic coupling afforded betweencoils 32 and 35 of control device l9 by the arm 36 as will now be morefully described.

When control device I!) is in the condition depicted in Fig. 1, minimumcoupling exists between coils 32 and 35 and the voltage induced in coil32 is at minimum value. Consequently, saturating winding 3i of reactor28 is afforded minimum energization with the result that the alternatingpotential of control electrode 23 is essentially 180 out of phase withrespect to the potential of anode 23 of tube 23. picts the relation ofthe potential of anode 23 (curve A) with respect to the potential ofcontrol electrode 23 (full line curve G) when the latter is displacedessentially 189 in time-phase therefrom. Consequently, tube 23 isthereby rendered non-conducting throughout its conducting half cycles.

Under the condition depicted in Fig. 1, motor 12 Will run at maximum ortop speed. With tube 23 rendered non-conducting throughout itsconducting half cycles, motor winding I2 is supplied with current whichis displaced substantially ninety degrees out of phase with respect tothe current supplied to winding l2 and at the same potential.

In the control system herein disclosed, the relationship of tension arm[3 and coupling arm 33 is such that as the length of the loop ll inthread ll decreases, due to an increase in the diameter of bobbin l0,arm 36 will be moved toward the position where it affords maximummagnetic coupling between coils 32 and 35.

As the coupling between coils 32 and 35 is increased, the alternatingpotential to which control electrode 23 is subjected is progressivelyshifted more into an in-phase relation with respect to the potential ofanode 23*, as depicted by broken line curve G in Fig. 2. Consequently,the conductivity of tube 23 is progressively increased. lhus the currentin the motor winding l2 is thereby altered in potential and changed inphase relationship with respect to the current in motor winding I2 andmotor I2 is caused to decrease in speed. When the condition of maximumcouplin obtainsin control device is, motor 52 will run at minimum speed.

The speed range of motor [2 may be varied between a top speed, whichremains essentially fixed, and a minimum speed which may be varied byadjustment of the adjustable resistance 21. Adjusting resistance 27 toinclude more resistance in circuit causes motor 12 'to operate at alower minimum speed.

The use of the current limiting resistor 24 in the anode circuit of tube23 is preferred in order to limit the peak current which may passthrough tube 23. This is desirable because it is possible to start tube23 conductingwhen capacitor 22 is charged to peak voltage.

Fig. 2 de- I claim:

1. In combination, an induction motor having a primary winding forsubstantially constant excitation and a second primary winding forvariable excitation, means to subject said second primary winding topotentials difiering in phase and amplitude with respect to thepotential impressed upon said first primary winding, said meanscomprising in series with said second winding and in parallel relationwith one another a capacitor and a gaseous electron tube having acontrol grid, a transformer comprising an input coil to be subjected toconstant alternating current excitation, an output coil, and means forvarying the magnetic coupling between said coils of said transformer,and a phase-shift network in circuit with said control grid forsubjecting the same to an alternating control potential varying in phaserelation with respect to the anode potential of said tube in accordancewith the degree of magnetic coupling between said coils of saidtransformer.

2. In combination, an induction motor having a primary winding forsubstantially constant excitation and a second primary winding forvariable excitation, means to subject said second primary winding topotentials differing in phase and amplitude with respect to the potential i mpressed upon said first primary winding, said means comprising inseries with said second winding and in parallel relation with oneanother a capacitor and a gaseous electron tube having a control grid, atransformer comprising an input coil to be subjected to constantalternating current excitation, an output coil, and means for varyingthe magnetic coupling between said coils of said transformer, and aphase shift network in circuit with said control grid for subjecting thesame to an alternating control potential, said network including asaturable reactor having its saturating winding supplied with rectifiedcurrent derived from said output winding of said transformer foraffording variation in the phase relation of said control grid potentialwith respect to the anode potential of said tube in accordance with themagnetic coupling between said coils of said transformer.

3. In combination, an induction motor havi a primary winding forsubstantially constant excitation, and a second primary winding forvariable excitation, means to subject said second primary winding topotentials differing in phase and. amplitude with respect to thepotential impressed upon said first primary winding, said meanscomprising in series with said second winding and in parallel relationwith one another a capacitor and a gaseous electron tube having acontrol grid, and a phase shift network for subjecting said control gridto an alternating control potential comprising a transformer having aninput coil subjected to constant alternating current excitation, anoutput coil, and means for varying the magnetic coupling between saidcoils of said transformer, a saturable reactor, means in circuit withsaid output winding and the saturating winding of said reactor forsupplying the latter with rectified current varying in value inaccordance'with the magnetic coupling between said coils of saidtransformer, said reactor by consequent variation of its saturatingcurrent serving to vary the phase of the control potential with respectto the anode potential of said tube.

' JAMES B. REEVES.

.: N references cited.

